One of the major problems confronting society today is the generation of waste. Municipalities, by their very existence, generate waste that must be disposed of and the problem is compounding continually. According to some studies, the average person generates four (4) pounds of municipal waste per day. Historically, rivers have been fouled with waste, swamps have been filled, and air polluted by waste being burned in open pits. Governmental agencies have become increasingly aware of the cumulative effects of these activities in recent years and have begun to mandate controls for the disposal of waste.
Landfilling is the primary method of waste disposal, which sometimes unfortunately reflects a mentality of xe2x80x9cout of sightxe2x80x94out of mind.xe2x80x9d When poorly contained landfills decompose, hazardous materials may find their way into the environment. Although technology is available to build safer landfills, there are fewer landfills today than here were ten years ago. It appears that landfills throughout the world are filling up.
The most commonly considered alternative to the landfill method is mass incineration and its related activity, the production of refuse derived fuel (RDF). Incineration and refuse derived fuel produce a variety of pollutants, which if improperly regulated or in high concentrations may cause respiratory discomfort and disease. These pollutants are believed to be caused by incomplete combustion of municipal solid waste and the combustion of plastics.
Solid waste products, often but not necessarily from municipalities (and so will be generically referred to herein as municipal solid waste or xe2x80x9cMSWxe2x80x9d), contain a tremendous amount of recyclable materials. Such materials include aluminum, iron, and diverse pulp and paper products. Environmentalists and public officials view the recycling of these materials as the most desirable method of waste disposal. According to some studies, however, curbside recycling has resulted in collection of only less than 10% of the recyclable materials. In addition to the lack of effectiveness, many people dislike the inconvenience of separating garbage, removing labels and lids, washing cans, bundling newspapers and other aspects of curbside recycling. In addition to the vast expense incurred in collecting recyclable curbside, money also must be spent on educating the public to use curbside recycling for it to be effective.
Thus there is a need to process MSW to recapture recyclable materials without the need for curbside recycling, without the need to spend funds to educate the public on its use, without the creation of harmful pollutants, and in an conically viable and repeatable industrial process.
The apparatus generally is comprised of a cylindrical vessel, containing at least one steam line for introducing steam into the interior of the vessel, and at least one valve for selectively releasing steam and/or pressure from the vessel during the process. The vessel further includes doors or hatches, or similar means to access the interior of the vessel for loading and unloading MSW. (The MSW may actually be transported to the vessel by a conveyor or other traditional means.) The apparatus includes a means for rotating the vessel, such as the use of trunnion rings and rollers, or chain-driven gear and sprocket system or xe2x80x9cspudxe2x80x9d ring. Any stable method of rotating the vessel at a controlled speed would be suitable. The interior of the vessel includes a structure for agitating the MSW as the vessel is rotated, such as a conical flighting or similar ridged or paddle-like structure. The apparatus further includes a boiler or other steam source for producing steam with which to heat and pressurize the vessel, and conventional steam lines, valves, and gauges for transporting, controlling, and measuring the flow of steam, temperature, and pressure. Optionally, the apparatus may include a water vamping apparatus, operatively connected to the release valve on the vessel, for evaporating and condensing the process discharge.
The process is summarized as follows. The vessel is preheated prior to loading to a predetermined preheating temperature. During loading, steam is fed into the vessel to maintain temperature, and the door at the far end of the vessel is shut during the loading process. After the vessel is loaded with MSW, the door through which the MSW was loaded is shut, steam is introduced continually into the vessel, and the vessel becomes pressurized. Fresh steam is continuously fed into the chamber from the loading end, and after a predetermined processing pressure is reached, steam is allowed to escape the chamber from the far end into the discharge steam line. The temperature and pressure of the vessel are monitored, and the flow of steam is regulated to keep the process within predetermined processing ranges (around 50 psi, 300xc2x0 F.). The vessel is rotated at a predetermined speed (depending on the size of the vessel), and after a predetermined amount of time (20 to 45 minutes), the pressure is released and the processed MSW is removed.